The Light Disc is a thrown melee weapon that stacks up to five, meaning up to five can be thrown at once (although this requires the crafting of five separate light discs). Its range is the longest of all thrown weapons. When thrown, it emits a miniscule amount of blue light. The Light Disc will bounce when it hits a wall. If used in

Player using multiple Light Discs

an enclosed area, it can bounce rapidly, making it extremely hard to dodge, this makes it quite an effective weapon.

The Light Disc has extended range when wearing armor that grants a melee speed boost. When wearing Hallowed Armor, the weapon can be thrown for about fifty blocks.

Notes

Only five can be thrown at a time, even when wielding multiple stacks.

Unless in an open area it is rare to have more than 4 discs out at one time. Keep this in mind if one doesn't want to waste extra materials.

The weapon cannot have prefixes upon crafting, nor can it be reforged.

When standing right next to any block and the weapon is thrown to the other side of the block, it will go through the block.

This could be a good strategy to fight The Destroyer since it deals more than 50 damage per second (with more than 1 Light Disc). The irony is that they're only craftable with the essence of the Destroyer.

Light Discs may impart some debuffs to the user when thrown against a nearby block too often on a server running in secure mode, due to extra anti-cheat methods used by that mode.

The player will be able to throw multiple Light Discs at once even if they have only crafted one. It is unknown if this is a bug or an intentional change.

Trivia

It may also be a reference to the side-scrolling NES platformer game, Shatterhand, where the weapon seen in this video of Shatterhand at around 8 minutes may resemble the Light Disc. As seen in the video, the sprite are comparable, the discs ricochets and the player can shoot multiple discs at the same time.

Light discs can be seen briefly as one zooms out to the mini map as the 'Loading' animation in the iOS version.

Bugs

Sometimes, when the player is standing by a one tile wide wall and throws the light disc, the light disc passes through the wall. This works with Boomerangs and the Magical Harp (1/2 of the time) as well.

If thrown correctly, it can often pass through blocks in random places.

Demonstrating how the disc can pass through closed doors and blocks.

When the Light Disc bounces off of a grass covered dirt block it produces particles as if it was boucing off Crimson covered dirt blocks.